DuPont Co. is experimenting with a polymerization process that could reduce the use of perfluorooctanoic acid, needed to make fluoropolymers.
PFOA, sometimes referred to as C8, might pose health risks. Elevated blood levels of the chemical recently were found in people living near DuPont's fluoropolymer manufacturing plant in Parkersburg, W.Va.
DuPont has been running a supercritical carbon dioxide reactor in Fayetteville, N.C., to investigate the new technology. The setup entails carbon dioxide under high pressure to dissolve monomers for making fluoropolymers. A supercritical material has properties between those of a gas and a liquid and is often a strong solvent. PFOA is not used in the supercritical process.
In conventional fluoropolymer polymerization, monomer is mixed with water and the mixture needs a surfactant such as PFOA to ensure the ingredients mix properly to polymerize. The process can lead to traces of PFOA in the resultant fluoropolymer or in wash water.
DuPont is using the supercritical process at Fayetteville to make limited quantities of a Teflon product, namely a fluorinated ethylene/propylene polymer, according to Dave Boothe, global planning manager for DuPont's fluoroproducts group. The polymer is melt-processable and mainly is used in high-grade electrical wire insulation and in release films.
``We're working to improve the utility of the process as we continue to explore its ability to produce a broader range of fluoropolymers for multiple applications,'' Boothe said in a news release. ``We estimate it will take a great deal more effort and time before even this single product is manufactured in commercial quantities. We believe the technology is worth pursuing because it could potentially be a simpler process, with fewer steps.''
DuPont installed the supercritical demonstration system for about $40 million in late 2000. The Wilmington, Del., firm is licensing the technology from the University of North Carolina, where researchers led by Joseph DeSimone invented the alternative fluoropolymer process.
``[The supercritical process] won't completely replace conventional technology,'' said DuPont spokesman Dan Turner in an interview. ``It is one element in our portfolio.''
Boothe said a number of constraints could frustrate broader adoption of the supercritical process. Many fluoropolymers have stringent technical specifications and if they are made by a new process it can take years to qualify them, he said. Polymers in aircraft and military applications, for example, have critical specifications.
Incentives for change
If DuPont finds the supercritical process does work well for a range of polymers, then the company needs to ask what incentives exist to spend huge sums of money to convert to the new process. Although the process can cut PFOA use in polymerization, DuPont has other ways of cutting PFOA emissions, Boothe said.
PFOA traces from fluoropolymer production are a small part of how it and similar chemicals can enter the environment. DuPont, a major producer of fluorochemicals, has multiple plans to limit their emissions. The company said it has cut PFOA emissions at its U.S. plants by 98 percent compared with 1999, and expects to achieve a 99 percent reduction in 2006.
DeSimone at UNC's Chapel Hill campus - who heads the early supercritical research - now is turning his attention to more environmentally friendly stain-resistant coatings for textiles and paper.
Conventional treatments based on fluorochemicals can degrade into PFOA. DeSimone's work uses smaller fluorocarbon molecules that are likely to be more environmentally benign. He described that work at the recent annual American Chemical Society meeting in Washington.
